What happens to my Outlook 2003 clients when I upgrade Exchange from 2003 to 2010 (SP1)

I have a single Exchange 2003 SP2 server and I am not planning the transition to 2010.

I am following Microsoft's guide to doing this process and it is very straightforward. I understand that I will still need personal folders, I know about the RPC issue but that it is resolved in SP1 which is why I'm using it (plus all of my clients use Cached mode anyway). However it doesn't answer a question that I am curious about.

I am building a new email server for Exchange 2010 as required and thus at the appointed time in the process I will transfer all of my mailboxes all at once from the 2003 Exchange Server to the 2010 exchange server.

All of my mail clients are Outlook 2003 and of course were configured to connect to the existing 2003 Exchange server. When I start moving mailboxes, what will happen to these clients.

The documentation I'm reading doesn't seem to really address this. Will the Outlook 2003 clients just know and understand that they need to connect to a new server? Will I need to go through and reconfigure them all?

In addition to this when I start this transfer will it take all of the mailboxes offline all at once, or will it do them one at a time, and as mailboxes are transferring, if users are connected via Outlook, what will happen to them.